MRI Scans Reveal Changes in Brain After Cold Water Immersion

MRI scans of the brain after a person is immersed in cold water explain why we may feel better after swimming outside or taking cold baths.

A research trial published in the journal Biology allowed for the first time to observe changes in the interaction between different brain parts following immersion in cold water.

A team of researchers recruited 33 healthy volunteers. After undergoing functional MRI (fMRI) scans, they immersed themselves in a pool of water at 68°F (20°C) for five minutes while an ECG and respiratory equipment measured their bodies’ physiological responses. After being quickly dried, they were given a second fMRI scan.

A comparison of the scans showed that changes had occurred in the connectivity between specific brain parts, in particular, the medial prefrontal cortex and the parietal cortex.

"These are the parts of the brain that control our emotions, and help us stay attentive and make decisions," said Ala Yankouskaya, Ph.D., senior lecturer in psychology at Bournemouth University in the U.K., who led the study.

The participants felt more active, alert, attentive, proud, and inspired and less distressed and nervous after immersing themselves in cold water. However, a reduction in negative emotions was not associated with changes in brain connectivity.

The researchers say this indicates that short-term whole-body immersion into cold water may have integrative effects on brain functioning, contributing to the reported improvement in mood.

Cold water therapy may carry health risks

Immersing yourself in cold water has been long practiced in the northern countries, while the former U.S. president Thomas Jefferson reportedly dipped his feet in a cold bath every morning to stay healthy.

In recent years, cold water therapy has come into the mainstream and has been praised for its possible health benefits, such as strengthening the immune system, improving cardiovascular circulation, and even increasing longevity. Cold water therapy may come in different forms:

  • When taking an ice bath, which is prepared by adding ice to water until the temperature drops to between 50°F and 59°F (10°C and 15°C), stay immersed for 10 to 15 minutes.
  • Cold whirlpool bath should last about 15 to 20 minutes at 50°F and 59°F (10°C and 15°C).
  • Stay under a cold shower at 50°F and 59°F (10°C and 15°C) for five to seven minutes.

Concrete research on how cold water impacts us is limited, but some studies associate it with several health benefits.

A 2005 study in young men showed that one-hour head-out immersions in cold water at 57°F (14°C) increased metabolic rate by 350% and dopamine concentrations by 250%. There was a 5% reduction in heart rate, while systolic and diastolic blood pressure decreased by 7% and 8%, respectively. Immersion was also associated with reduced levels of cortisol, also known as the stress hormone.

A study from the Netherlands demonstrated that taking cold showers reduced absent days from work by 29%.

A narrative review from 2020 suggests that swimming in the water below 41°F (5°C) may have a positive impact on cardiovascular risk factors such as lipid profile or blood pressure, a positive effect on insulin metabolism, and can even be anti-depressive. Winter swimmers are also considered to be more resistant to certain illnesses and infections, such as those affecting the upper respiratory tract.

Cold plunges may also carry some risks. For example, cold shock caused by water at 50-60°F (10-15.5°C) may kill a person in less than a minute, according to the National Center for Cold Water Safety, a Canada-based non-profit organization,

As water temperature falls from 70°F to 60°F (21°C to 15°C), controlling breathing and holding breath becomes progressively more difficult. Meanwhile, a water temperature of 50-60°F (10-15°C) can lead to total loss of breathing control.

Moreover, being in cold water triggers hypothermia — a dangerous drop in the body’s temperature — faster than just being out in the cold. This is because water takes heat away from the body 25 times faster than air.

Plunging into cold water is also at your own risk. Maybe colder dips sound appealing to you and investing in a cold plunge bath is something worthwhile. Regardless, do your research and stay safe when jumping into the unknown.

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